Add JsonUtils::isValidJson

.gitignore

@@ -1,4 +1,6 @@
 /.php-cs-fixer.cache
+/.phpunit.result.cache
 /composer.lock
 /tags
 /vendor
+/.idea

src/Json/JsonUtils.php

@@ -88,6 +88,22 @@ public static function roundTrip($value)
         return self::decodeArray(self::encode($value));
     }
 
+    /**
+     * Checks if given string is a valid JSON document.
+     *
+     * If you want to validate JSON before decoding it for further usage, decode
+     * it right away and handle JsonUtilsDecodeException instead, as it is way
+     * more efficient.
+     */
+    public static function isValidJson(string $json): bool
+    {
+        if (function_exists('json_validate')) {
+            return json_validate($json);
+        }
+
+        return json_decode($json, true) !== null || JSON_ERROR_NONE === json_last_error();
+    }
+
     /** @return mixed */
     private static function decodeInternal(string $json, bool $assoc)
     {

tests/Json/JsonUtilsTest.php

@@ -59,4 +59,23 @@ public function testDecodeArrayFailure(): void
         $json = '"hello';
         JsonUtils::decodeArray($json);
     }
+
+    public function testIsValidJson(): void
+    {
+        $json = '{"hello":"world"}';
+        self::assertTrue(JsonUtils::isValidJson($json));
+    }
+
+    public function testIsValidJsonNull(): void
+    {
+        $json = json_encode(null);
+        self::assertIsString($json);
+        self::assertTrue(JsonUtils::isValidJson($json));
+    }
+
+    public function testIsValidJsonFailure(): void
+    {
+        $json = '';
+        self::assertFalse(JsonUtils::isValidJson($json));
+    }
 }